Electric-motor control.



D, G. JACKSON. ELEUTRIG MOTOR CONTROL.

APPLICATION TILED APR.14,1906.

Patented June 8, 1909.

2 SHEBTS-SHEET l.

m 6 W z m w I). 0. JACKSON. ELEGTRIG MOTOR CONTROL. APPLICATION FILED APR.14, 1906.

Patented June 8, 1909.

2 SHEETS-SHEET 2.

ZEUGIZZ OW waif/$65565.

i A, y Y A a X a J W DUGA'LD O. JACKSON; OF MADISON, WISCONSIN,

WILLIAM-B. JACKSON, OF MADISON,

ASSIGNOR To DUGALD c. JACKSON AND WISCONSIN, A (.OPARTNERSHII ELECTRIG-MOTOB. CONTROL.

Specification of Letters Patent.

Patented June 8;, 199,9.

Application filed April 14,1906. Serial No. 311,641.

To all whom it may con cern:

Be. it known that I, DLGALD C. JACKSON citizen of the United States, residing at Madison, in the county of Dane and State of 'isconsin, have inventeda certain new and useful Improvement in Electric-Motor Control, of which the following is a full, clear, concise, and exact description, reference being-had to the accompanying drawings, forming a part of this specification. 1

My invention relates to the operation and protection of electric translating devices, and particularly to the operation and protection of electric motors during the starting period.

My invention relates to that type of arrangements in which a starting rheostat is divided into various sections, each section being controlled by switch so operated that the sections are successively rendered inetl'ective after the main switch for the motor circuit has been closed. The electromagnetic switches which sevcr ally control the sections of the starting rheostat are connected in suitable relation with the main circuit, the arrangement being such that the switch elcctromagnets, with the ex ception of the first one, are not'cnergized until after the first one has performed its Function of removing the corresponding rheostat section from the circuit of the motor armature. Each electromagnetic switching mechanism controlsthe circuit condition of the magnet in the following mechanism, and as each mechanism becomes etl'cctive to remove its rheostat section from circuit. the magnet in the 'l'ollo\ ving mechanism is en crgized and in turn becomes etiective to remove its 'rheostat section from circuit,-and so on until all of the rheostat has been removed from circuit and the motor connected directly with the main circuit.

The invention particularly relates to means for preventing the mechanisms from introducing current into the motor too rapidly, so thatthe motor may be allowed to normally accelerate its load without an excessive starting current; and the means for producing this desired result include devices foi automatically checking the actuation of the electromagnetic mechanisms or t'or restoring them to their normal condition in reverse order (if the current flow becomes excessive during the process starting the motor) until the current returns to a "suitable value, and then permitti the normal an elcctrmnagnetic motor circuit.

starting procedure to continue. Protection against oxres'sive currents is also afforded after the motor has been started. Various arrangements and devices may be employed for carrying out my and in the accom 'ianying drawings I illustrate two arrangements.

Figure 1 shows an arrangement in which the various electromagnets for the switching mechanisms are adapted to be'included se rially in circuit and may be successively short circuitcd by additional electro 1n-1g-. netic switching mechanism, controlled hythe amount of current flowing through the circuit, in case of excessive current flow in the Fig. shows an arrangement in which the 'arious switch electromagnets are included individually in bridge of the line, the additional electromagnetic switching mechanism being adapted to open the individual electro nagnet circuits when the current in the lfiOi'fil CllClllt exceeds a predetermined value.

The motor M is shown as a shunt wound motor, and the main switch S serves when closed to connect the field F of the motor directly with the supply circuit 1 through the conductors 2 and 2-3, and to connect the armature A of. the motor with the supply circuit through the mnductors 2 and 4, the conductor -l-i11ititllly including the resistance sections R. R, R and I? of the starting resistance. and the conductor 2 includes the winding W of the electromagnetic switch controlling mechanism 1). Associated with the resistance sections R, R 13 and l, respectively, are electromagnetic nechai'iis ns S. S, S and Si respectively; whose windings w, w w and w are connected serially together and with the main line limbs through the conductors 5 ductor 5 normally including the switch arm 7 and contact part 8, this arrangement being that shown in Fig. 1. The electromagnetic mechanisms may be made up in any,

desired manner, but, as illustrated, the winding thereot'is surrounded by ,an iron sheath /z, and a plunger or core v ciprocation-within the winding. Each electromagnct may have a cap 0 having a conical recess a. into which the conical end of the core 1' engages upon attraction thereof,

and when the core is in this, position the magnets are capable of maintaining the SWlt'Cil mech nism m proper position with invention,

and 6, the con-- is adapted for rc-V the lever is adapted for engagemcnt'with a much less current than was necessary to at first move thecore. and switch mechanisms into the proper position. The switch levers Q Z, ,1 and Z are provided for the respec tive electromagnets and pivoted at an interposition, and a resistance B may, tlltlltinlt,

mediary point to the cores' thereof, each lever being pivoted at one end 2 and connccted with one terminal of the correspond- 'ing reslstance section, while the free end ot j contact part designated by the letters 1;, which contact part is connected with the pivot point. of the lover of the following electromagnet and also with the adjacent terminals of the corrcspomling resistance sections.

Near the free. end of each lever is a tongue 1 designated by the letters c, being insulated from the arm and adapted upon movement I of the ,arm by the clectromagnet. to engage.

a switch levcr designated by the letters 11 which normally engages a contact anvil designated by the letters f, the lever arm (Z being moved away from the corresponding anvil 7' upon upward movement of the lever Z. Each of the contact anvils connected with the conductor (3 including the electromagnets, while the arms (Z are connected with the common conductor 9 connecting with the main line limh and a short circuit is closed about the elcctronmgnets that i rent flows to the line limb 3 and normally follow the firstelectromagn'ct S.

The operation of the system. thus tar is as follows:.Upo'n closure of the switch S curflows through three paths, to the conductor Qback to the main switch. One path but through the field i The other path includes all the resistance sections R R R- and R and the armature A in series. And

1, this direct. path preventing energizing current from flowing through the following relays. The motoris now in condition to start. and electromagnet S beconnng energized causes engagement of the lever Z w th 5 the contact part?) to short circuit the resistance section B and allows the motor armature to accelerate its speed. At; the same time also the switch arm (Z is raised from the anvil f and the current flow is extended I to the second electromagnet S and from there through the switch parts (Z and f to the conductor 9- and limb This second electromagnet in turn becomes energized and its switch arm Z actuated to short cir- 0 cuit the section R from the armature, circuit, at the same time tisengaging switch parts 03* and f to extend the current flow to the third electromagnet, and so on until all in circuit through the various switch arms. Owing to the magnetic circuit arrangement of the electromagnel's,as described, current will be required to hold the cores in an actuated position than to move them to such be included in the electromagnet circuit to allowjust enough current to continuously ilow therethrough to maintain proper control of the switching parts, and this resist ancc may normally be short circuitcd trom circuit by the switch parts (Z 7 controlled by the switch lover I. Mechanisms such as the dash pots Z may be suitably arranged and adjusted to retard the movement of the switch levers l to any desired degree. as they arw attracted by the connected core.

There may be times during the starting of the motor when the controlling mechan- "isms may operate to introduce the current into the motor too rapidly, or during the operation of the motor after starting, the current tlow may suddenly become excessive, and the additional electromagnetic coutrolling mechanism E is provided to readjust the circuit conditions under these circumstances to reduce the current to a safe value. This additional clectromagnetic mechanism comprises the winding lV sun rounded by the magnetic shell 10 having a stationary .core part 11 to be engaged by the core 12 after attraction thereof, whereby less current is required to hold the core than to cause. its motion. The upper stem 13 from the core carries a switch blade l t for engaging at one end with a contact strip 15 connected with the limb 2 and at the other end adapted for engaging successively with the contact plates 16, 1? and 18 connected respectively with the contact. anvils f, f and f of the electromagnetic switching mechanism. Atthe end of the upward movement of the core 12, the stem 13 engages the switch arm 7 to raise this arm from the contact part 8 which is connected with the limb 3. ridash pot 19 is connected with the lower stem 20 of the core and is adjusted to suitably retard the upward movement of the core but to allow a nick return thereof. The winding W and associated parts are of such dimensions that there will be no upward movements of the core 12 when the current through the motor is within a predetermined maxinnun value. but when the current exceeds this maximum value the core will begin to move upwardly.

Suppose that the motor is overloaded on the resistance sections have been short cirupward attraction of the core 12. if, for 55 ended and the armature connected directly l instance, upon starting the motor the curltl lltl

seems Q rent became excessive when resistance scc tion Rfwas removed, the contacthlade 14 would move upward until, coming into engagement with the contact rent ,would be withdrawn,

Flats 17, thecurro m the electromagnet S and diverted through the short number of electromagnets current to a safe va lu'e. the motor is. thus the inertia .to restore the The armatnre on given time to overcome 'otthe loalditis brought to appropriate speed without injurious .eifects.

Themotor isv thus protected without interfering with the process of starting except that ,the process is forcihly delayed to a suitable degree for the purpose of affording the motor time to overcome the inertia oat effective.

its load.

It will be noticed that the ,ele ctromagone ate. time in reverse order if thearmaexcessive during the process of starting the motor, lllltll the current, returns to a su table value, and the normal procedure of controlllng the rheostat resistancesections then continues from the switch last opened. Thus, the system is. at all times kept in perfect balance. Even after. the motor has been started and is running, excessive current How may cause sufiicient ectuation of the electromagnetic mechanism Eto control a netic mechanisms are renderedv ineffective suiiicient number of electromagnetic switches until the current is restored to. normal value.

I n Fig. 2, the arrangement is slightly different flOIlllllilh shown in Fig. 1. Instead )eing' connected to be serially included in the controlling circuit, the electromagnetic mechanisms S S S and S? are adapted to be connectedseparately in brid' e of the line limbs, s: 1 ch c on11ection of kl-1C1 mechanism being controlled by the preceding mechanism. Also, instead of short circuiting the mechanisms, the electromagnetic mechanism E i'satlap'ted foropening the various ener gizing circuits to render the mechanisms in- The switch arms Z Z Z and P are connected, as in F l, to short circuit the corresponding rhecstat sections it, R ll angl R}, upon attraction of the cones 0ndii'igelectromagnetic cores. The arms d'?, (1 and 4 are pivoted alcove the electromagfrom the .electroinagn'et .3

short circuits. only a sufficient the switch lei er d nets heengaged by a stemfrom the upper nfiho f the core and thereby ,to henioved frtun )l()1'lllfll, position of engagement with the contact p'arts g,,g-.',gf and gtto analter- 'i'r e positionot engagement with the eonta c t parts Zr}, .lp1- ,,/z a 2yl. /L I The contact art g of the electromagnetic mechanism S reconnected w th one term nal of the, windl 1g. l(-l 21l,l (l t rough ,a res stance device m with the line lin hl; and the switch level" r1 iiorinally also conne The alternate conta ,part 71- connects with of the following conl t p i I 5 troll ng gnechan ism and also connects through a r s t an ce devices Withthe normal contact party" and with a terminal of the wmdts, with the line limb 3.,

i gwflof this following mechanism. The

te riiate co ntact part llconnects with the switch lever .df a ncl tl n'oug resistance (191 viqepf with the ormal contact part and a tcrm inal ottho winding 0 of the next following electromagnetic mechanism, and

so on throughoutany number thereof. The other terminal of the winding w co nnet-ts through condl ictor 22 with the contact part 23 over, which is arranged the contact arm il connected w1tl'rt11e limb The otlngr terminal of winding w? connects tl' rough conductoi 25 with the contact part 26 over which is arranged the contact. arm 27: (x ninected with linelimh 2. Theother te 'niinal of. findingw connects through conductor and arm 39 with the limb-2, whilethe other terminal of winding 10* connects through condlwtoi .31; through contactpart 3 2 and alrin {33 with line li nh 2, andso on throughout th ries of electromagnetic mechanisms.

Vai ms mechanical arrangementsmay be devised foi' c lisengag'ing the arn'is2 i,27, 3 0

aud t- 3 from their associ ted contact parts at pilo g er I times,' and I have diagrammat cally shown certain; ineansfior accomplishing this. ,flfhe engls ofthe arms, asshown, are an-aimed to engagetlhy the steps 34;, 35, 36 115,237 carried. by the stem 38 extending from thecore 12 andso arranged that, upon attra ction f the core,. the a1-111| 33 will be first engaged anddiscminected from its con-' tact gart; associated with the last electrom agnetic mechanism Si, and, the arms 30. 27 and 24-will he successively engaged by the steps tiltj tO lfg. 12 continues to risei An arrange 1n nt, mayhe provided for opening themain @{CIllh'QffQI' .openi ng all of the clrc u'it's for tlieelectro nagngaic mechanisms, and lhave shown a circuit-breaker switch alrmBQpi'y- Died at, oam having an arm eldisposed in tliepatli of the step 42 to engaged-by th s ,tfephnd (liSengagcd from its normal .1 i I I contactatflfii, thereby to open the line limb 2 mac thus the main circuit V v 1 Under normal conditions in th s system,

28 and through contact part :29 e

upon closure of thelmain switch S the current passes from the limb 3 tothe limb 2 t1 rough three paths, one containing the field winding F, another including all the rheostat sections'and the armature A, and the third path including the switch lever al contact part g, winding 20, conductor 22, contact part 23 and arm 24'. The electromagnet 5 becomes energized and causes movementof the arm Z to short circuit the correspond ing rheostat section R and the arm (Z is moved from contact with g to make contact with 71 The resistance coil as is now included in circuit with the winding of, as less current is needed to maintain the core of S in its actuated position. Upon engagement of this arm (Z in contact with 9 current also fiows from the limb 3 directly to the arm (Z of the next controlling mechanism and from contact party to winding Z02, conductor 5, contact part 26 and arm 27 to the limb Resistance section R then becomes short circuited and arm 03 moved into engagement with k to allow current to flow to the next electromagnet, and resistance device m is included in circuit with one winding 4,0 to reduce the current flow after actuation of the mechanism. The electromagnetic mechanisms S and S are similarly controlled in successive order, until all the resistance sections of the main rheostat are short circuited and the armature connected directly withthe main circuit. Z, P, Z and Z* may be modified by retarding mechanism such as dash pot arrangements Z, and the movements of the core 12 may be modified by a dash pot arrangement 19 adjusted to retard the upward movement of the core but to'allow quick return thereot'. lit during the course of these operations to stop the motor the current should become excessive and beyond the fixed maximum the electromagnetic mechanism E becomes effective and the core 12 and switch actuating steps are carried upwardly to successively open.

the various switches and circuits-through the controlling mechanism windings, this deenergizes the controlling mechanism in reverse order to maintain the balance of the system. assumes a safe value, the core 12 is released and the normal starting procedure continues until the motor is connected directly with the supply circuit. As the core is attracted upwardly, the step 34 and arm 33 are first brought into engagement and the arm disconnected from its contact with 32 to thereby open the circuit through the winding w of the last controlling mechanism. lf the core continues to move upwardly. the step 35 diseugages arm 30 from its contact with 2) and the circuit through winding w opened. i And thus the various mechanisms The movement of the arms it the current very shortly again I operates verse order to reinclude the rheostat sections in circuit. If the current persistently remains abnormal this will continue until all the rheostat sections are again included in circuit, and the core 12 finally is wholly attracted and the main circuit opened upon engagement of the step 4L2 with the extension 4. 1 and consequent opening of the switches 39, 43.

Under the system of controlling herein described and illustrated the motor is at all times under protection against excessive current flow and this protection is particularly afforded during the starting period when the dangers from overload and excessive current flow are greatest. The protection without interference with the process of starting, the process being merely held in check or delayed for a suitable period to give the motor time to over come the inertia of its load and to allow the current flow to assume a safe value. The system is at all timesmaintained in perfect balance at any stage of the operation and is entirely automatic.

As changes in the arrangement of the apparatus and circuits may readily be made without departing from the spirit of my invention, I do not wish to be limited to those described, but

I claim as new and desire to secure by Letters Patent:

switchin the main circuit, means controlled. by the magnets after energizat-ion ot the first magnet whereby said magnets are successively connected with the main circuit, and electromagnetic controlling means associated with the circuits of the electromagncts for causing successive disconnection thereof from the main circuit and in reverse order.

3. The combination of a plurality of electromagnets, circuits therefor for connecting said magnets with a main circuit, one of said magnets being energized upon closin a switch in the main circuit, means contro led by the magnets after energization of the first magnet whereby said magnets are successively connected with the main circuit,

are rendered inettective 'one by one in re- .and electromagnetic mechanism controlle by the current flow through the main circuit for causing disconnection of said electromagnets from the main circuit in reverse order to that of their connection therewith. 4. The combination with a main circuit, of a plurality of electromagnets connected therewith through branch circuits and adapted upon closure of a switch in the main circuit to become successively energized from the main circuit, an electromagnetic mechanism included in the main circuit, said electromagnetic mechanism being normally ineffective and adapted upon excessive current flow through the main current to change the branch circuits to cause the electromag nets to become successively, disengaged from the main circuit in a reverse order. ,5. The combination with a main circuit, of a larai'ity'of electromagnets adapted to be connected therewith through secondary circuits, each electromagnet with the exception of the first being normally rendered inefi'ective by mechanism controlled by the preceding electromagnet, said that electroniagnet being adapted to become eltectivc upon closure of a switch in the main circuit whereby the mechanism controlled thereby is actuated to render the second electromagnet effective and whereby each succeeding electromagnet is likewise rendered effective until all-the electromagnets have become effective, and additional mechanism independent of the mechanism controlled by the electromagnets for causing said electromagnets to be rendered ineffective in reverse order.

6. The combination with a'main circuit of a plurality of electromagnets adapted to be connected therewith through secondary circuits, each electromagnet with the excep- 40 tion of the first being normally rendered ineffective by mechanism controlled by the preceding electromagnet, said first electromagnet being adapted to become effective upon closure of a switch in the main circuit whereby the mechanism controlled thereby is actuated to render the second electromagnet effective and whereby each succeeding electromagnet is likewise rendered efi'ective until all the electromagnets have become effective, and additional electromagnetic controlling mechanism operating independently of the mechanism controlled by the electromagnets to render the electromagnets successively ineffective in reverse order. 7. Theccombination with a main circuit, of a plurality'bi. electromagnets adapted for connection therewith, a switch for-connecting the main circuit with a supply source, circuit changing means controlled by each electromagnet and normally disposed to render the succeeding electromagnet ineffective, one of said electromagnets being adapted to be actuated upon closure of said switch whereby its circuit changing mechanism is actuated to cause the succeeding electromagnets and the circuit changing mechanisms 1 controlled thereby to be successively actuated, and controlling electromagnetic mechanism and circuit changing mechanism to be actuated ereby to cause the electromagnets order. r

8. The combination with a main circuit, of a plurality of electromagnets, circuit changing mechanism for each electromagnet associated with the next electromagnet to normally render all but one of said clectromag nets ineiiective, means upon closure of a switclrin the main circuit-for causing actuation of the one electrdmagnet whereby its circuit changing mechanism becomes actuated and the succeeding electromagnets rendered eli'cctive one by one, a controlling electi 'omag'net, circuits controlled thereby. and circuit changing mechanism controlled by said main electromagnet and associated -withv the other clectromagncts, actuation of said main electromagrnct causing the circuit cl'ianging mechanism controlled thereby to render the electromagnets ineffective one by one and in a reverse order.

S. The combination with a main circuit, of a-plurality oi clcctron'iagnets, one of said with the main circuit upon closure of a main switch, the other electromagncls being normally rendered ineffective, means controlled by the clectromavgnets and adapted upon connection of the one electromagnet with the main line to cause effective current flow to be lead successively to the other electromagnets, aid cor rolling electromagnetic mechanism for withdrawing the effective current-flowsuccessively from the electromagnets and in reverse order.

10. Thecombination with a main circuit,

electromagncts being adapted for connection with the main circuit upon closure or a main switch, the other electroniagnets being normally rendered ineifective, means controlled by the clectromagncts and adapted upon connection of the one electromaguet with the main line to cause effective current flow to be lead successively to the other clectroumgnets, and electromagnetic governing mechan ism controlled by the current fiow in the main circuit and adapted upon cm: H ive current liow thcrethrough to become active to cause withdrawal of effective current flow from the electron'iagne'ts to cause said electromagnets to become ineffective in a reverse order. Y

11.. The combination with a main circuit, of a plurality of electromagnets for connection therewith, one of which magnets may be energized upon closure of a switch in the 'maii'i-circuit, means controlled by the magto again become ineliective and in reverse of a plurality of elcclromagnets, one of said clectromagnets being adapted for connection nets to cause the magnets to be successively connected to become successively ettect-ive, means for reducing the current flow tl'irough the electromagnets after said magnets have become effective, and main electromagnetic controlling means for causing electromagnets; to be rendered ineffective in a reverse order.

12. The combination with a main circuit, of a plurality of electroinagnets for connection therewith, one of which magnets may be energized upon closure of a switch in the main circuit, means controlled. by the mag nets to cause the magnets to be successively connected to become successively effective, means for inducing the current fiow through the electromagnets after said magnets have become efi ective, and main electromagnetic mechanism controlled by the current flow in the main circuit and adapted upon current flow by a predetermined value to become l active to render the electroniagnets successively inettective in reverse order.

13. In an electric motor controlling system, the combination with a motor, of a rheostatnormally all in circuit therewith, a plurality of electromagnets,each associated with a section of said rheostat, a circuit for each electroinagnet controlled by the preced ing clectroinagnet and normally rendering all the electromagnets ineliective except one thereof which is adapted for connection with the. main line upon closure of a switch, connection of the one electromagnet with the main line causing actuation thereof to re move its rlieostat section from the motor circuit and to cause the circuits for the following clectroniagnets to be successively changed to render the electron'iagnets suc- (ft .sivcly ell'ective whereby the rheostat sections are successively removed from the motor circuit, a main electromagnetic controlling mechanism governed by the current liow through the motor and ineffective upon normal current flow, said main electromagnetic mechanism upon current flow beyond a predetermined value causing a. change in the circuit conditions of the electroinagnets to render said electromagnets ineffective in succession and in reverse order.

14. The combination of a plurality of similar electroinagnet's, circuits therefor for connecting said magnet-s with a main circuit,'

one of said magnets being energized upon closing a switch in the main circuit, means controlled by the magnets after energization of the first magnet whereby said magnets are successively connected with the main circuit, and controlling means for causing disconnection of said electromagnets in reverse order. I

15, The combination with a main circuit, of a plurality of similar electromagnets for connection therewith, one of which magnets may be energized upon closure of a switch in the main circuit, means controlled by the magnetsto cause the magnets to be successively connected to become successively efi'ectv ive, means for reducing the current flow through the electroi'nagnets after said mag nets have become effective, and main electromagnetic controlling means for causing electromagnets to be rendered ineffective in a reverse order.

16. The combination of a plurality of similar electromagnets, circuits therefor for connecting said magnets with a main circuit, one of said magnets being energized upon closure of a switch in the main circuit, means one of said magnets being energized upon closing of a switch in the main circuit, means controlled by the magnets after energization of the first ii'iagnet whereby said magnets are successively connected with the main circuit, controlling means for causing discon- .nection or". said electromagnets in reverse order, a translating device supplied by the main circuit, and current flow ad uSting resistances for the device, resistances being controlled by said electremagiiets.

18. The combination of a main circuit, a plurality of electroinagnets, one of said electromagnets being adapted for direct connection with the main circuit upon closure of a switch, the other clectroinagnets being successively connected each in an independent bridge of the main circuit after actuation of the first eleotromaguet, the connection of each electroniagnct being controlled by the preceding electromagnet, and additional means for controlling the electroinagnet circuits and adapted upon actuation to successively open these circuits for the elec tro nagnets whereby said electroinagnets become disconnected from circuit in reverse cuit, and means for including a resistance.

camera p in circuit with each electromagnet after con.-

nection thereof in circuit.

20. The combination with a main circuit, of a plurality of electromagnets normally disconnected therefrom, one of. said electromagnets being adapted for direct connection in bridge of the main circuit upon closure of a switch, means controlled by the electromagnets for causing the other electromagnets to become successively connected eachin an independent branch of the main circuit, and a normally short circuited resist ance for each electromagnet adapted to be included in circuit therewith upon actuation thereof.

21. The combination wit la main circuit,

of a plurality of electromagnets normally disconnected therefronnone of said electromagnets being adapted for direct connection in bridge of the main circuit upon closure of a switch, means controlled by the electromagnets for causing the other electromagnets to become successively connected each in an independent branch 0t themain circuit, a resistance for each electromagnet circuit, a short circuit normally about each resistance, and means controlled upon actuation of an electromaguet to open said short circuit aboutthe corresponding resistance, whereby said resistance is included in the electrcma netcircuit.

22. The combination with a main circuit, of a plurality of electromagncts normally disconnected therefrom, one or" said electromagnets being adapted for direct connection in bridgeof the main circuit upon closure of a switch, means controlled by the electromagnets for causing the other electromagnets to become successively connected each in an independent branch of the main circuit, and additional controlline mechanism for causing disconnection. of the electromagnets from circuit in reverse order.

23-. Thecombination with a main circuit, of a plurality of electromagnets normally disconnected therefrom, one of said electromagnets being adapted for direct connection in bridge of the main circuitupon closure of a switch, means controlled by the electromagnets for causing the other electrom'agnets to become successively connected each in an independent branch of the main circuit, and additional mechanism controlled by the current flow through the main circuit adapted to be actuated upon sufiicient current flow to open the electromagnet circuits in an order reverse to that. of their closure.

2%. The combination with a main. circuit, of a plurality of electromagnets normally disconnected therefrom, tine of said electromagnets being adapted for direct connection in bridge of the main circuit upon closure of a switch, means controlled by the electro-.

magnets forcausing the other electromagnets to become successively connected each in an independent branch of the main circuit, and additional electromagnetic controlling means adapted to successively open the electromagnet circuits in reverse order.

.25. The combination with a main circuit, of a plurality oi electromagnets normally disconnected therefrom, one of said electromagnets being adapted for direct connection in brid s or the main circuit upon closure of a switc 1, means controlled by the electromagi'iets for causing the other electromagnets to become successively connected each in an independent branch of the main circuit, additional electromagnetic controlling means adapted to successively open the electromagnet circuits in reverse order, and to cventu ally open the main circuit.

26. The combination with a main line, of a plurality of electromagncts having one terminal connected with one line limb and the other terminal normally disconnected from the other line limb, one of said electroinag nets being adapted to have its other terminal connected directly with the other line limb upon closure of a switch, means upon actuation of the one electromagnet for causing the other terminal of the next electromagnet to be connected with the other line limb, means upon actuation of the second electromagnet for causing the other terminal of the third elcctromagnet to be connected with the other line'limb and so on until all the electromagnets have been connected successively in bridge of the line limbs in a certain order, and additional mechanism adapted to successively disconnect the first terminal of the electromagnets of the first line in reverse order to the connectionv of the other terminals of the electromagnets with the other line limb.

27. The combination of a sectional rheostat, an electromagnetic switch for each section, means associated with each switch mag net except the last for bringing the succeedin g magnet into operation upon the actuation of its own switch, and a master magnet for successively deiinergizing the switch ma nets when the starting current becomes excessive.

28. The combination with an electric motor, of a starting rheostat controlled by a plurality of successively energized magnets, each of the said magnets being arranged to bring its successor into operative excitation upon actuating its own rheostat switch, a

master ma' net connected in the motor circuit, and means associated with the master magnet for successively deenergizing the switch magnets when the current becomes excessive.

29. A plurality of electromagucls and a master elect-romagnet, combined wit h switches controlling the energizing sir-(nits of the said electromagnets, sald master magnet causing In Witness whereof, I hereunto subscribe operation of the said SFV'itChGS successive my name this ninth day of April A. D., 1906. rder when the current in the winding of the DUGALD Q JACKSON. master magnet exceeds a predetermined value, and causing restoration of the switchee \Vitnesses:

-as the curren't in the Winding of the master E. G. HonFEn,

magnet falls #m its normal value. f I)ORA E. CASEY. 

